Feldt



(No Model.) I

N. H. BORGFELDT.

- SGREW PROPELLER.

u, PEIERS. Mmm m Wnhinim nv c.

the deck of the vessel. 1

UNITED STATES PATENT OFFICE.

NICHOLAS H. BQRGFELDT, OF NEW YORK, N. Y.

SCREW-PROPELLER.

SPECIFICATION forming part of Letters Patent No. 285,002, dated Feptember 18, 1883, Application filed November 24,1882. (N0 model.)

To all whom it may concern.-

Be it known that I, NIOHOLAS/ H. Bone- FELDT, of New York, in the county and State of New York,.have invented an Improved Screw-Propeller, of which the following is a specification. A

Figure 1 is a side'view of my improved screw-propeller; Fig. 2, aface View of the same; Fig. 3, a central section thereof; Fig.4. a face view of a propeller of different form, having my invention; Fig. 5, a side view of the same.

The object of this invention is so to construct screw-propellers for ships as to prevent the formation of a suction-vacuum behind each propeller-blade. I have ascertained that ordinary propellers are moved through the water with a degree of speed greater than the motion of the water resulting from its gravity or endeavor to find a level, and that, consequently, a vacuum is formed behind each revolving propeller-blade, which vacuum tends to delay the rotary motion of the blade and retard the action of the propeller. This suction-vacuum exists on the backing side of the propeller-blade when the propeller is in motion. If this suctionvacuum can be destroyed by the admission of air, its retarding influence upon the propeller will'be overcome, and the action of the propeller made the more effective upon the ship to which it is attached. The result of such a destruction of the suction-vacuum will be that a propeller of a given size, driven with the full power of an engine, and propelling aship with a certain speed when the vacuum is in existence, will, when the vacuum is destroyed, increase the velocity of the ship, and where such a result does not flow from the destruction of the vacuum it will be because the propeller working with the vacuum is too small for the ship, so that a larger propeller can be used by the same engine on the same vessel with improved result, provided my invention is applied thereto;

My invention consists in carrying air, by the action of the propeller alone, through or along the propeller-blade to the point which is threatened with the vacuum, so as to destroy the suction-vacuum, and at the same time providing the'air-supply pipeleading to this propeller-blade with an adjustable valve or means of regulating the amount of air admitted from In the accompanying drawings, the letterA represents a screw-propeller, having blades a, boss b, and metallic cap d fastened onto the boss. This screw-propeller is mounted upon a shaft in theusual manner, and hung as serew propellers have always been hung, or in any suitable manner. B is an air-pipe leading into the cap (I, and carried upward by preference along the rudder-post G. The propeller-blades a are channeled or hollowed, and have apertures e on the backing sides of their blades,

. only preferably near the edges. The hollows of the blades and the apertures c communicate through the boss Z) and cap (I with the pipe B. Theupper end of the pipe-B extends above deck and in the neighborhood of the wheelhousein fact, I prefer to cause it to enter the wheel-house, so that it shall be under the control of the man at the wheel; At this upper end the pipe has a suitable valve, f, or stopping device, by means of which the amount of air allowed to it can be regulated at will.

The form of propeller to which my invention is applied is immaterial. It may either be such form as indicated in Fig. 2, or such as shown in Fig. 4., or any other form. propeller is revolved, the air will be drawn by the propeller through the pipe B and apertures a, so as to fill whatever space the water can not fill with sufficient rapidity behind the rapidly-'revolvin g propeller-blade. By this means the draw-backofsuction usually suffered is is entirely obviated, its effect on the ship done away with, and the entire driving force of the propeller utilized. My experiments have satisfied me that in the neighborhood of twenty per centum of force' will be gained by the destruction of the vacuum that is caused on the backing side of the propeller-blade of ordinary construction.

When my invention is applied to apropeller, the same canbe abouttwenty per centum larger in area than the propeller of ordinary construction that would be adaptable to a given vessel under the standing rules,or should have a coarser pitch to'the extent of about twenty per centum.

I do not regard the manner of fastening the pipe B, or the direction of its course, as at all material to my invention. It may be caused to communicate with the central portion of the screw-propeller in suit-able manner, and

As this ICO may be supported'or held in place in any suitable manner.

Instead of makin g the blades hollow, as shown, they may be suitably channeled or provided with pipes or conduits that lead to the apertures e.

I do not claim drawing water through propeller-blades, which interferes with their motion by its centrifugal action; nor do I claim forcing air through such blades by separate contrivances.

I claim- A screw-propeller whose blades have airchannels and apertures e on the backing side, combined with the air-pipe B, leading upward to the deck of the vessel, and with the regulating appliance f on the upper part of said pipe, all arranged for drawing air automatieally to the backing side of the propeller by its rotation, as set forth.

NICHOLAS H. BORGFELDT.

\Vitnesses:

XVILLY G. E. SCHULTZ, WILLIAM H. 0. SMITH. 

